1. Field of the Invention
The present invention relates to pneumatic pressure controllers, and more particularly relates to a blind pressure pilot apparatus wherein a continuous stream of instrumentation gas is interrupted by movable indicating arms mounted directly to a bourdon tube which arms move in an arcuate path responsive to changes in pressure producing rotation of the bourdon tube.
2. General Background and Prior Art
In the operation of chemical plants, and similar industrial complexes, there is a need to maintain certain elements of the industrial system or device in a certain position.
As an example, it may be desirable to keep a valve open and a pipeline as long as the pressure within the pipeline is above a certain value or below a certain value. In a like manner, it may be desirable to maintain a valve in an open position as long as a desired minimal temperature is maintained and as long as a desired maximum temperature is not exceeded. As long as there is a suitable device for the measuring of such a parameter as temperature pressure or the like, these values can readily be measured and the devices can be used to trigger the valves or like devices in the event that the parameter exceeds desired operating range. Bourdon tubes are often used for the measuring of pressure in pneumatic systems such as is seen in the case of gas instrumentation. It is to this general field that the present invention is directed.
The present invention utilizes a suitable parameter responsive device such as a bourdon tube to operate a responsive sensor which can shut off a desired system such as a valve, in the event that a desired maximum or desired minimum parameter such as excessive or inadequate pressure is reached.
Controllers are broadly known, it is known to operate controls by means of various parameters such as pressure or temperature. In the prior art, a source of control area is utilized in many instances to keep a certain control mechanism in an operative position. When a desired maximum or minimum condition is achieved, the control it shifts to close a valve are similar systems. Many prior art type controls require a constant and/or tightly controlled input of control area in order to operate properly. If the input of control air varies greatly, the system will fail.
Applicant's co-pending prior patent application (U.S. Ser. No. 874,429, entitled "On-Off Control Movement") provides a control mechanism which does not require a certain tightly controlled input of control air in order to operate the instrumentation properly.
The present application provides a pressure responsive indicator such as a bourdon tube to which is directly mounted without movable linkage a pair of indicating arms which directly rotate with and responsive to the expansion of the bourdon tube which produces a rotation.